Cowgill's law[1] says that a PIE laryngeal /h₃/, and possibly /h₂/, turns into /k/ in Proto-Germanic when directly preceded by a sonorant and followed by /w/.
[citation needed] This law is still controversial, although increasingly accepted.
Donald Ringe (2006) accepts it;[1] Andrew Sihler (1995) is noncommittal.
[2] Examples are fairly few: The first two examples, however, have good alternative explanations which don't involve Cowgill's law: If the sound law becomes generally accepted, the relative chronology of this law could have consequences for a possible reconstructed phonetic value of /h₃/.
If /h₃/ was a voiced labiovelar fricative as is occasionally suggested, the change would therefore have been: /ɣʷw/ > /ɡʷ/.